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Types of Bacteria and Shelf-Life of Evacuated Carbon Dioxide Injected

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Types of Bacteria and Shelf-Life of Evacuated Carbon Dioxide Injected 218 Journal ofFood Protection Vol. 42. No.3. Pages 218-221 (i\1arch.1979) Copyright 1979, International Association of Milk, Food, and Environmental Sanitarians Types of Bacteria and Shelf-Life of Evacuated Carbon Dioxide­ Injected and Ice-Packed Broilers J. S. BAILEY1,2•, J. 0. REAGANl, J. A. CARPENTERl, G. A. SCHULERl andJ. E. THOMSON2 Food Science Department, University ofGeorgia, Athens, Georgia 30602, and Richard B. Russell Agricultural Research Center, United States Department ofAgriculture, Science and Education Administration, Downloaded from http://meridian.allenpress.com/jfp/article-pdf/42/3/218/1649927/0362-028x-42_3_218.pdf by guest on 27 September 2021 P.O. Box 5677, Athens, Georgia 30604 (Received for publication June 29, 1978) ABSTRACT microflora on spoiled stored pork were Pseudomonas or Broiler carcasses were packed in low-permeability film bags that Achromobacter. Clark and Lentz (8) found that in were evacuated, injected with C02 , then held at 2 C. Broilers were vacuum-packaged beef held at 5 C, the Pseudomonas examined microbiologically and for off-odor to determine the shelf-life and the Moraxella-Acinetobacter group were inhibited and types of bacteria. Vacuum level did not significantly affect by 15% C02 • Shank and Lundquist (29) showed that the bacterial counts. Broilers stored in 65"7o C0 had a 1-day longer 2 spoilage of vacuum-packaged cured meats involved lactic shelf-life than those held in 20o/o C02 and about a 5-day longer shelf-life than ice-packed broilers. Spoiled carcasses from either 20 or acid bacteria almost exclusively. Patterson and Gibbs 65% C02 packages had an acid-sour off-odor, and more than 90% of (23) found that lactobacilli were the predominant the bacteria present were Lactobacillus. Ice-packed broilers had the spoilage bacteria on beefthat was vacuum packaged and typical putrid off-odor at spoilage, and more than 95% of the bacteria held at 0-2 C. Pierson et al. (24) found that 95% of the were non-pigmented Pseudomonas. bacteria on anaerobically packaged beef were lacto­ bacilli. Lactobacillus and other lactic acid bacteria whose growth is not significantly inhibited by C02 have a direct Kraft (19) listed 24 genera of bacteria as isolates from bacteriostatic effect on many gram-negative bacteria (14) poultry and Cox (9) found one additional genus. Only a and on three strains of Pseudomonas and one strain of few genera, however, affect the acceptability and Salmonella typhimurium (25). shelf-life of poultry meat. Most observers found many In this study we aimed to determine the effect of C02 different types of bacteria at the time of slaughter, but on and vacuum on types of bacteria on broilers in carcasses that were held aerobically at 0-5 C the commercially feasible, bulk shipping packs of low Pseudomonas or Achromobacter groups predominated permeability film, and to determine the effect of this at the time of spoilage (1,3,5,15,22.23). microf1ora on shelf-life and olfactory quality of broilers. Coyne (12), Haines (16), Ogilvy and Ayres (22) and Scott (28) found that the two principal spoilage organisms Pseudomonas and Achromobacter were MATERIALS AND METHODS inhibited by C02 • Average generation time for A "Conofresh 4000" packaging system (Continentia! Forest Pseudomonas apparently was reduced as a logarithmic Industries - Corrugated, Greenwich, CT)4 was used to package 560 function of C02 level (22). Haines (16) and King and broiler carcasses in a simulated commercial evacuated, C02 -flushed bulk pack. Chilled broilers were taken from the drip line at a Nagel (17) found that C02 levels of 20 to 70% doubled the generation time for Pseudomonas if other environ­ commercial processing plant and placed four to a plastic film bag (7 cc/100 in2 , permeability); then bags were placed into a wax coated mental factors were constant. Thomson (32) found that corrugated box for insertion into the packaging chamber. The chamber psychrotrophs were inhibited by 10 and 20o/oC02 • was evacuated to 10, 17 or 24 inches of Hg. Carbon dioxide was The predominant spoilage microorganisms on beef injected into a film bag to either 20 or 65%, and the bag was sealed. stored in air were Pseudomonas and Achromobacter Percentage of C02 in each bag was not measured directly, but was (2,18,26). Gardner et al. (13) found that 96% of the based on extrapolation from the known pressure applied by the C02 injection mechanism; the pressure required to produce each C02 content with this packaging equipment had been determined 1 University ofGeorgia. previously. The packs were held at 2 C and sampled for 2 Russell Agricultural Research Center. microorganisms and for off-odor after S, 9, 12, 15 and 18 days of 3 The eighth edition of Bergey's Manual of Determinative Bacteriology now classifies Achromobacter as Acinetobacter. storage. Controls consisted of broilers that were packed in ice and held 4 Mention of specific brand !Ulmes does not imply endorsement by the in wax-coated corrugated boxes and stored at 2 C. Controls were also authors or the U.S. Department of Agriculture to the exclusion of sampled microbiologically and for off-odor after 5, 9, 12, 15 and 18 others not mentioned. days of storage. All treatments were duplicated. BACTERIA AND SHELF-LIFE OF C02-PACKED BROILERS 219 For total plate counts a 12.3-cm2 area of breast skin was swabbed 13----El CONTROLS 8 with calcium alginate swab which then was dissolved in a sterile 9.9-ml • 20% C02 1 o/o sodium citrate blank. Appropriate serial dilutions were made, • ~ 65% C02 plated in duplicate on Plate Count Agar (Difco) and plates were 7 / incubated for 48 h at 30 C. Counts were expressed as log1 0 /em'. After sampling, carcasses were discarded and a new bulk pack was opened on each sampling day. Carcasses were evaluated for off-odor when packs were opened for "':E 6 ~~ microbiological sampling. Sampling was terminated when the carcasses u became spoiled, as determined by strong off-odor. Strong off-odor had Q: IJJ become apparent on the carcass at a count of log 6.5 which, therefore, a.. 5 was defined as spoilage. r I- _;;r-~ All data were analyzed by the Statistical Analysis System of Barr and z :::> Goodnight (6). Significance was determined by the F-test and a 0 4 G-d difference was considered significant at the 5o/o level of probability. u ~~ A total of 375 isolated colonies were picked from countable plates <{ Downloaded from http://meridian.allenpress.com/jfp/article-pdf/42/3/218/1649927/0362-028x-42_3_218.pdf by guest on 27 September 2021 and generically classified with the identification schemes of Q: Biochemical Tests for Identification of Medical Bacteria 1)0), and IJJ 3 Bergey's Manual of Determinative Bacteriology (7). Thirty colonies I-u were picked from two plates each day that packs were opened for <{ m evaluation. For control samples, 15 colonies were picked from duplicate 2 plates on sampling days. A statistical randomizing procedure 0 (!) employing a numerical grid (10) and a random numbers table (30) was 0 used to obtain a representative sample ofthe colonies from each plate. _J Colonies were transferred to brain heart infusion (BHI) broth (Difco) and incubated at 25 C for 48 h. BHI plates were streaked for isolation and then incubated at 25 C for 18 to 24 h. Isolated colonies were 0 picked. checked for purity and then tested for: gram reaction and 3 6 9 12 15 18 morphology, motility, and catalase and oxidase reaction. We then did the additional tests which were necessary for generic identification. The biochemical characteristics that identified each genus were as follows: DAYS OF STORAGE IN BULK PACK (a) Micrococcus - gram-positive, catalase-positive cocci, no growth in 15% NaCI, no growth in 40o/o bile and Voges Proskauer-negative; (b) Figure 1. Total aerobic bacterial counts of broilers packaged in Staphylococcus- gram-positive, catalase-positive cocci, growth in 15o/o vacuum in bulk packs containing 20 and 65o/o CO, and of ice-packed NaCI. growth in 40o/o bile and Voges·Proskauer-positive; (c) controls. All birds were stored at 2 C. Lactobacillus- gram-positive, catalase-negative non-sporeformingrods, no reduction of nitrate, no true branching (a representative sample of before birds stored in 20% C02 and about 5 days before Lactobacillus isolates was confirmed by use of Lactobacillus- 50 strips - birds stored in 65%C02 • At the time of spoilage, control API); (d) Bacillus- gram-positive, catalase-positive, sporeforming rods; carcasses had the typical putrid off-odor that was {e) Microbacterium thermosphactum -gram-positive, catalase-positive, characterized by Ayres et al. (3). nonmotile rods, methyl red-positive and growth on STAA agar (14); If! Corynebacterium - gram-positive, catalase-positive, non-sporeforming The bacterial population of evacuated packaged rods, H 2S-negative, gelatin liquefaction-positive; (g) Pseudomonas broilers with C02 injected into packages was pre­ jluorescens - gram-negative, catalase-positive rods, oxidase-positive, dominantly Lactobacillus (Tables 1, 2). Packs containing motile, slow growth at 37 C, no growth at 41 C, no reduction of nitrate, 20o/o C02 showed a mixed microflora and Lactobacillus no fermentation of dextrose, fluorescent pigment produced; (h) constituted 53 o/o of the bacteria on day 5 of storage; non-pigmented Pseudomonas - gram-negative, catalase-positive rods, motile, oxidase-positive, aerobic acid production from dextrose, no Lactobacillus constituted not less than 97 o/o of the anaerobic fermentation of dextrose, no pigment produced; {z) microflora thereafter (Table 1). After 18 days of Acinetobacter (formerly Achromobacter) gram-negative, catalase· storage, broilers were spoiled and 100o/o of the bacterial positive rods, oxidase-negative, indole-negative, H2 S-negative. RESULTS AND DISCUSSION TABLE 1, Percent of isolates recovered from broilers held in vacuumized shipping packs containing 20o/o C0 and stored at 2 C.
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